The present invention relates to display drivers, electro-optical devices, electronic equipment, and a gamma correction method.
Electro-optical devices represented by liquid crystal display (LCD) panels have come to be increasingly mounted on the portable electronic equipment. On the other hand, image displays rich in color tone have been demanded, as multiple gray-scale images have been generalized.
In general, the gamma correction is applied to a video signal for performing the image display according to the display properties of a display device. The gamma correction is performed by means of a gamma correction circuit. In an electro-optical device as an example, a gamma correction circuit changes the voltage level itself that corresponds to gray-scale data for determining a gray-scale value, for example, to change the driving voltage so that desired display properties can be obtained. Examples of the method for changing voltage level are disclosed in JP-A-2003-233354, JP-A-2003-233355, JP-A-2003-233356 and JP-A-2003-233357.
It is sometimes desired to perform a gamma correction that differs depending on color components, that is, the R component, G component, and B component constituting one pixel. This is because the display properties may differ depending on color component. However, a plurality of voltages with the resistance divided by a resistive circuit have been regarded as reference voltages, and a data voltage has been selected among these reference voltages. In these cases, the gamma correction has altered the voltage level by altering this resistance division ratio. Accordingly, if such a gamma correction circuit is provided for each color component, the gamma correction circuit involves a problem of increasing the circuit size as well as increasing the current spent in the resistive circuit 3 times more than otherwise.
Different gamma corrections need to be performed between the case where a displayed image of the LCD panel is seen indoors and the case where the displayed image of the LCD panel is seen in the outside light. It is therefore desirable that a manner of performing a gamma correction can be changed flexibly.